I linked that engine because I just read about it last night and found it interesting. It should get better efficiency with much less weight.
How much of the time does the best designed engine spend in it’s peek torque band? Not much, which means that the engine will not provide advertised efficiency. Fuel cells are about 60% efficient now, absolute, not Carnot, and the energy not converted into electricity is rejected as high quality heat. Perfect for thermoelectric conversion since you brought it up.
“How much of the time does the best designed engine spend in it’s peek torque band?”
Depends on the application.
For a diesel in stationary applications, almost all the time. For diesels in train applications, most all of the time. For diesels in a direct-coupled automotive application, at highway speeds with the cruise control on, it will spend quite a lot of time at or near peak torque if we have a transmission that wasn’t designed by morons. eg, my Ford Navistar engine is quite efficient at 65MPH, which is just about 1900 RPM. That’s about 100RPM above the peak torque hump. The most efficient internal combustion engine in the world extant is a maritime two-stroke diesel with about 52% thermal efficiency. It burns bunker C fuel.
Assumptions of proper transmission technology obviously excludes GM immediately from discussion, so let’s not worry about them right now, but I digress.
The European diesel sedans are adding more gear ratios to their transmissions all the time. Benz is supposed to have a nine speed transmission under development for their new diesels. Audi has a eight speed. Ag tractors have increasingly gone to IVT/CVT’s, which allow them to run the engine at just above peak torque RPM’s all the time, maximizing efficiency. The same could easily be done in automotive applications.
However, if we assume the existence of a series hybrid drivetrain, then a diesel can be run at the best point on the fuel/torque curve all the time. Let the electrical half of the drivetrain worry about varying the drivetrain speed, then the diesel gets to operate at its most efficient.
The truth is this: the most efficient internal combustion engine technology we have at our disposal right now is a turbocharged diesel with a computerized fuel rack. Most all the other ideas extant either cannot develop their ideas in an economically feasible package (eg, Stirling engines), or they’re just not competitive (eg, Miller, Atkinson cycle engines). I could whip out a design for a hybrid diesel auto on several sheets of paper right now, with existing technology, for a car that would get 80MPG on the highway and I would not need to get into bleeding-edge aerodynamic design or ultra-technical body/frame materials (eg, carbon fiber). We’d just be talking about steel and aluminum body/frame components, a hybrid setup, a modest battery, regen braking, etc. In other words, rip the engine out of a Prius, dump in a diesel and call it good.
Distractions with all electric cars, or “zero emissions” and other such nonsense has been preventing us from getting to a point where a good, but not perfect, design doubles the US fleet mileage ratings.
The perfect is the mortal enemy of the good. And far too many non-engineers have been polluting this issue with their goofy goddamn ideas for the last 20+ years, along with telling us of all the conspiracy theories of “300 MPG carburetors” and other technology that the oil companies have “bought and buried.” I would dearly love to see the US simply put a stake in the ground and say “We want to achieve a fleet efficiency of X MPG by year T and deliver it at the average auto sales price +/- 10%” and then give the problem to engineers and tell everyone else to shut up and quit pretending that they know anything. Don’t tell us that it needs to be or can’t be “zero emission” or “hydrogen” or “natural gas” or any other such BS. Just tell us mileage and delivery date. Then tell everyone else (environmentalists, politicians, auto writers and all manner of dreamers and fools) to STFU.
Then we could finally make some progress.
BTW, in case you think I’m full of crap in my 80MPG estimates, check out the latest Audi effort which is similar in idea. I didn’t know this had been unwrapped until after I posted the previous message:
http://www.greencarcongress.com/2010/10/etronspyder-20101001.html
107 MPG (US gallons). And it will blow the doors off most sports cars. And it doesn’t look like some boring Detroit sedan or some idiotic Japanese econo-box.
It looks fast, it IS fast, and it is efficient.
Meanwhile, we’re listening to a bunch of patchouli-oil soaked morons who carp and whine endlessly about “zero emissions” who inspire such nonsense as the GM Volt, which was the original topic of this thread. The GM Volt will probably get over 40MPG on the highway. Let’s say it gets 50MPG.
Whoopti-freakin’-do.
Compared to this Audi, GM has labored mightily and brought forth.... boredom.
I know the idea of a diesel hybrid would work. Now. Today.
The Germans are proving me right.
And GM continues to deliver absolutely boring shite. At my expense, because I’m paying taxes.